Ah... I understand. The 3 axis full kit order button simply populates a shopping cart with the items needed. It will put in 3 Linistepper kits. Simple change the quantity to 4 and press enter. The shopping cart will apply the same discount to the 4th. It will also suggest other optional items that you might want like the parts for the relay driver.
James hosts the single best wiki page about steppers for CNC hobbyists on the net:
http://www.piclist.com/techref/io/steppers.htm Disagree? Tell him what's missing! ,o)